This was my mistake.
The solution is (followed by document https://openedx.atlassian.net/wiki/spaces/COMM/pages/2603816700/Maple)
- In LMS admin dashboard. Navigate to lms_domain/admin/waffle/flag/
- Add flag courseware.use_legacy_frontend
- Add flag course_home.course_home_use_legacy_frontend
- Restart lms and cms
- Try to access course page
